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United States Patent |
5,179,927
|
Henke
,   et al.
|
January 19, 1993
|
Injection-type combustion engine with electric spark ignition and a
heating system
Abstract
The invention relates to an injection-type combustion engine having an air
intake duct for each cylinder, a fuel injection valve and a heating
element arranged downstream of it in the air intake duct.
In order to achieve a simple installation for the heating element, the
cylinder head has an opening through which the heating element can be
inserted such that its heat sink is arranged to be largely self-supporting
in the cross-section of the air intake duct.
Inventors:
|
Henke; Jurgen (Wernau, DE);
Spinner; Erwin (Leinfelden, DE);
Fruh; Peter (Weinstadt, DE)
|
Assignee:
|
Mercedes-Benz AG (DE)
|
Appl. No.:
|
767903 |
Filed:
|
September 30, 1991 |
Foreign Application Priority Data
Current U.S. Class: |
123/549 |
Intern'l Class: |
F02M 031/00 |
Field of Search: |
123/549,547,557,552,543
|
References Cited
U.S. Patent Documents
3930477 | Jan., 1976 | Jordan | 123/549.
|
4350134 | Sep., 1982 | Sparks | 123/549.
|
4967706 | Nov., 1990 | Van Wechem et al. | 123/549.
|
5007402 | Apr., 1991 | Scherenberg | 123/549.
|
5048500 | Sep., 1991 | Curhan | 123/549.
|
5056495 | Oct., 1991 | Yamashita et al. | 123/549.
|
5086747 | Feb., 1992 | Curhan | 123/549.
|
Foreign Patent Documents |
0453927 | Oct., 1991 | EP | 123/549.
|
3426469 | May., 1986 | DE.
| |
3921739 | Nov., 1990 | DE.
| |
2567965 | Jan., 1986 | FR.
| |
0219446 | Feb., 1985 | JP | 123/547.
|
6155256 | Mar., 1986 | JP.
| |
6155357 | Mar., 1986 | JP.
| |
Primary Examiner: Kamen; Noah P.
Attorney, Agent or Firm: Evenson, Wands, Edwards, Lenahan & McKeown
Claims
We claim:
1. An injection-type combustion engine with electric spark ignition,
comprising at least one cylinder head provided with an air intake duct, at
least one intake valve provided in the cylinder head, at least one fuel
injector, and a heating element mounted downstream of the at least one
fuel injector as viewed in a direction of intake air flow and having a
heat sink configured as a hollow flat box and at least one PTC-pellet
associated therewith, wherein the heating element is inserted through an
opening in a wall of the air intake duct so as to project into the air
intake duct such that a wall of the box configured heating element extends
transversely with respect to the intake air flow and has at least one fin
projecting away from the box configured heating element to extend
substantially in parallel to the intake air flow in the air intake duct
and having a surface facing the fuel injector such that the fuel is
sprayed onto the surface of the fins facing the fuel injector.
2. A combustion engine according to claim 1, having two intake valves per
cylinder, one dividing wall dividing the fuel mixture intake pipe into two
halves which each lead to an intake valve, and the heating element is
situated in the profile of the dividing wall just in front of this
dividing wall as viewed in the direction of the intake air flow.
3. A combustion engine according to claim 1, the at least one fin is
arranged on the exterior side of the heating element.
Description
BACKGROUND OF THE INVENTION
This invent relates principally to an injection-type combustion engine with
electric spark ignition which comprises at least one cylinder equipped
with an air intake duct, at least one intake valve provided in the
cylinder head, at least one fuel injector, and a heating element mounted
downstream of this injector and having a heat sink and one or several
PTC-pellets mounted on it.
A combustion engine of this type is known from the German Patent Document
DE-C-34 26 469 and from the Dutch Patent Document NL-A-8801334.
It was found that of the total exhaust gas emission approximately 50%
occurs during the short time period in which the engine has not yet
reached its operating temperature. Even exhaust gas catalysts which, under
normal conditions, reduce the amount of exhaust gas by approximately 90%
do not reach this degree of conversion before the operating temperature of
the catalyst has been reached. The conversion starts at a temperature of
approximately 300.degree. C. so that, after a cold start, the exhaust gas
emission of the engine in a catalyst is not reduced or hardly reduced.
Since the temperature level is not high enough for evaporating the fuel
(gasoline or alcohol), an additional amount of fuel must be supplied when
the engine is cold in order to obtain a combustible mixture. This leads to
a high exhaust gas emission. Therefore, when the engine temperatures are
low, the fuel consumption and the exhaust gas emission are relatively
high. By the preheating of fuel / air mixture, a considerable amount of
fuel is therefore also saved because less fuel or no additional fuel is
injected. In the case of the initially mentioned combustion engine, the
fuel is sprayed onto the heating element which is brought to the desired
temperature within a very short time and in the process is also brought to
the desired temperature. As a result, the fuel will evaporate better, and
a better mixture with the combustion air is also obtained. The heating
element is switched off when the engine is warm enough to take over the
evaporation of the fuel.
In the case of the engine known from the mentioned German Patent Document
DE-C-3426469, the heating element has the form of a pipe which projects
into the intake duct of the cylinder and is surrounded by an insulating
pipe. The pipe and the insulating pipe are provided with an edge flange,
the edge flanges being situated in a recess of the cylinder head and being
fixed by the air intake pipe. This construction has the problem that the
mounting and exchanging of the heating element is a time-consuming
operation. The same problem exists in the case of the engine according to
the Dutch Patent Document NL-A-8801334 where the heating element is
integrated in a plate which is clamped in between the intake duct and the
head of the cylinder.
SUMMARY OF THE INVENTION
It is an object of the invention to avoid this problem and to provide an
engine of the initially mentioned type in which the heating element can
easily be mounted and exchanged and in which, in the case of a
multi-cylinder engine, the heating elements can be exchanged for each
cylinder. The invention also has the object of improving the transmission
of the heat from the heat sink to the fuel.
According to the invention, the initially mentioned injection-type
combustion engine for this purpose is characterized in that the heating
element is mounted through an opening in the wall of the cylinder head or
of the air intake duct such that the heat sink projects into the fuel
mixture intake duct.
In order to achieve an excellent heat yield without significantly
increasing the flow resistance of the air flow, the heat sink is provided
with one or several fins which extend approximately in parallel to the air
intake flow and at an angle with respect to the intake fuel flow.
The invention is extremely well suited for an injection-type engine with
two intake valves per cylinder, in which case a dividing wall divides the
intake pipe for the fuel into two halves which each lead to an intake
valve. In the case of an engine of this type, there exists the danger that
in the cold condition the fuel condenses on the cold dividing wall. This
danger is avoided according to the invention by inserting the heat sink
into the profile of the dividing wall just in front of this dividing wall.
The invention will now be explained in detail by means of the figures.
BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 is a sectional view of the part of a combustion engine according to
the invention;
FIG. 2 is a top view of the heating element and of the dividing wall in the
fuel/air mixture duct, the interior surface of the intake ducts for air
and the fuel being represented by uninterrupted lines;
FIG. 3 is a view of the heating element.
DETAILED DESCRIPTION OF THE FIGURES
The part of an injection-type engine illustrated in FIGS. 1 and 2 comprises
an air intake duct 1 which is fastened to a cylinder head 2 such that it
connected to a duct 3 in order to inject a fuel/air mixture by way of two
intake valves 4 into the cylinder.
An injector 5 for the injection of the fuel which is connected to a fuel
feeding duct 5a is fastened to the air intake duct 1.
A dividing wall 6 is cast into the duct 3 and, as illustrated in FIG. 2,
ends in a wedge shape in the upstream direction and divides the duct 3
into two partial ducts 3a, 3b.
In order to bring the fuel to the desired temperature when the engine is
cold, this fuel is sprayed onto a heating element 7 during the injection.
This heating element 7 projects through an opening in the cylinder head
into the duct 3. It is not impossible that the heating element 7 projects
into the air intake duct 2 through an opening, naturally at a point where
the injected fuel comes in contact with the element 7.
The heating element 7 comprises a heat sink 8 in the form of a hollow flat
box which is arranged in the profile of the dividing wall 6 just in front
of its upstream end, and has PTC-pellets 11 associated therewith.
On the exterior side of the flat heat sink box, two oblique fins 15 are
cast on which, as illustrated in FIG. 1, in the mounted condition of the
heating element, extend in parallel to the air flow direction indicated by
the arrows. However, the feeding direction of the injected fuel extends so
obliquely with respect to the fins 15 that the fuel is sprayed onto the
fins. As a result, it is achieved that the heat transmission from the heat
sink 8 to the fuel takes place very efficiently without significantly
increasing the resistance against the air flow.
Additional advantages of the described construction are that the heating
element can be manufactured in a simple and cost-effective manner and can
be mounted and exchanged very easily.
Variants are possible within the scope of the invention. The invention is
also applied to an engine having a single intake valve for each cylinder
but it is particularly advantageous in the case of an engine with two
intake valves for each cylinder.
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